This invention relates to an alarm system designed to prevent the theft of electrical or electronic devices such as computers, printers, olscilloscopes and similar devices which can be rather expensive to replace. More particularly this invention relates to a motion sensitive alarm device which, when incorporated in a computer, or like device; is adopted to emit an audible alarm or signal when the device is wrongfully moved.
There are currently available in the marketplace a number of devices which are designed to deter the theft of rather expensive electronic equipment, such as computers and the like. Some such devices are designed physically to secure the equipment against removal, while others, which may or may not be employed in combination with the aforementioned devices, are designed to produce a warning signal if an effort is made to effect unauthorized removal of the equipment. A variety of such signaling devices are disclosed in U.S. Pat. Nos. 3,484,775; 3,710,371; 3,766,540; 3,836,901; 4,284,983 and 4,327,360.
Of particular interest are the U.S. Pat. Nos. 3,710,371 and 3,836,901 and 4,284,983, each of which suggests using some means to detect whether or not the protected device has been wrongfully moved, and if so, to emit a warning signal. The first of these three patents suggests using a mercury switch to sense unauthorized movement of the associated device and to trigger an alarm. The disadvantage is that once the alarm is energized it is latched in its operative mode until shut off by a special key. The devices disclosed by the latter two Patents have the additional advantage that they function to produce an alarm only upon disconnecting the associated equipment from a power source, and upon wrongful movement of the equipment.
Such prior switch devices however, have proved to be unsatisfactory in many respects. In the case of the device disclosed by the U.S. Pat. No. 3,710,371, for example, any innocent movement of the associated equipment causes a false alarm to be emitted. In the case of the U.S. Pat. Nos. 3,836,901 and 4,284,983, each alarm is latched in an operating mode once it is energized. Also, the device of U.S. Pat. No. 4,284,983 requires a special oscillator circuit to provide a pulsating signal to an alarm, and a battery recharging circuit and a special monitoring circuit are necessary for determining whether or not the power is being supplied to the recharging circuit for the battery.
It is an object of this invention, therefore, to provide an improved computer alarm system of the type described which is substantially more compact, reliable and inexpensive to manufacture than prior such systems.
Another object of this invention is to provide an improved, motion sensitive computer alarm system of the audible type, which will automatically shut off at a predetermined time after unauthorized movement of the computer has ceased.
It is a further object of this invention to provide an improved system of the type described which is produced in a quantity of modular sections which can be releasably coupled with one another to complete the alarm system for a computer or the like.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompany drawing.